The way to add shadow to frame?

I am making an attempt so as to add Shadow to the Border of the UIButton, however it isn’t working. Shadow ought to as seen in picture, however precise requirement is like UIButton will probably be in clear background, and shadow round border. So how can I obtain it?

  class GlowButton: UIButton {  
        
      non-public let borderGlowLayer = CAShapeLayer()  
        
      override init(body: CGRect) {  
          tremendous.init(body: body)  
          setup()  
      }  
        
      required init?(coder: NSCoder) {  
          tremendous.init(coder: coder)  
          setup()  
      }  
        
      non-public func setup() {  
          backgroundColor = .clear  
          layer.masksToBounds = false  
          clipsToBounds = false  
            
          borderGlowLayer.fillColor   = UIColor.clear.cgColor  
          borderGlowLayer.strokeColor = UIColor.clear.cgColor  
          borderGlowLayer.lineWidth   = 2.5  
          borderGlowLayer.shadowOffset  = .zero  
          borderGlowLayer.shadowRadius  = 0  
          borderGlowLayer.shadowOpacity = 0  
          borderGlowLayer.masksToBounds = false  
          layer.addSublayer(borderGlowLayer)  
      }  
        
      override func layoutSubviews() {  
          tremendous.layoutSubviews()  
          layer.masksToBounds = false  
          clipsToBounds = false  
          borderGlowLayer.body = bounds  
          borderGlowLayer.path  = UIBezierPath(roundedRect: bounds, cornerRadius: 20).cgPath  
      }  
        
      override func didUpdateFocus(in context: UIFocusUpdateContext, with coordinator: UIFocusAnimationCoordinator) {  
          tremendous.didUpdateFocus(in: context, with: coordinator)  
          coordinator.addCoordinatedAnimations {  
              if self.isFocused {  
                  self.borderGlowLayer.strokeColor  = Colours.focused_border.cgColor  
                  self.borderGlowLayer.shadowColor  = Colours.focused_border.cgColor  
                  self.borderGlowLayer.shadowRadius  = 12  
                  self.borderGlowLayer.shadowOpacity = 1.0  
              } else {  
                  self.borderGlowLayer.strokeColor   = UIColor.clear.cgColor  
                  self.borderGlowLayer.shadowOpacity = 0.0  
                  self.borderGlowLayer.shadowRadius  = 0  
              }  
          }  
      }  
  }